This week, I mainly practised creating skeleton, using the female character which was modelled by Yann.
When I was creating skeleton, after I clicked on the button ‘Bulid AdvancedSkeleton’, something went wrong. The knee joint didn’t face to the right direction. Even I tried to rebuild, the orientation was still incorrect.
After that, I asked Luke about why this happened and he replied to me very quickly. The reason why this happened was the knee was not far enough forward to define which direction the leg was pointing. There should always be a bit of bend in the knee to allow the IK pole vector to calculate which direction the bend is prominent.
After refinement, the skeleton was correctly built.